3× x-45=15
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a: =4(3h15'+2h4')=4(195'+124')=1276'
b: =3(15'45s-6'45s)=3x9'=27'
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Đáp án:
15 x 3 +(45 – 15 x 3) = 45 + (45 – 15 x 3)
= 45 + (45 – 45)
= 45 + 0
= 45
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(36 × 27) : 3 = 36 × (27 : 3)
= 36 × 9
= 324
--------
(125 × 15) : 5
= 125 × (15 : 5)
= 125 × 3
= 375
--------
(15 × 12) : 9
= (5 × 3 × 12) : 9
= 5 × (36 : 9)
= 5 × 4
= 20
--------
450 : (3 × 5)
= 450 : 15
= 30
--------
(45 × 63) : 9
= 45 × (63 : 9)
= 45 × 7
= 40 × 7 + 5 × 7
= 280 + 35
= 315
![](https://rs.olm.vn/images/avt/0.png?1311)
\(45\cdot y-30=12\cdot15-40\cdot3\)
\(\Rightarrow45\cdot y-30=180-120\)
\(\Rightarrow45\cdot y-30=60\)
\(\Rightarrow45\cdot y=60+30\)
\(\Rightarrow45\cdot y=90\)
\(\Rightarrow y=90:45\)
\(\Rightarrow y=2\)
\(\Leftrightarrow45y-30=60\Leftrightarrow45y=90\Leftrightarrow y=2\)
![](https://rs.olm.vn/images/avt/0.png?1311)
TL :
( 15 x 15 ) : 2 x ( 15 x 15 ) : 2 x ( 15 x 15 ) : 2 + ( 0 + 1 + 2 + 2 + 3 + 45 ) x 0
= 0
=> vì : tất cả số nào nhân vs 0 đều = 0
_HT_
\(3\times x-45=15\\ =>3\times x=15+45=60\\ =>x=\dfrac{60}{3}=20\)
3.x-45=15
3x=15+45
3x=60
x=60:3
x=20